Certain fluid systems can require protection against backflow from e.g., a drainage or sewage system. For example, a dishwashing appliance is typically connected to a drain line leading to a sewage system for allowing wastewater from cleaning operations to be fed to the sewage system. However, under certain conditions, waste fluid may attempt to backflow undesirably from the sewage system into the drain line and into the dishwashing appliance. By way of additional example, certain water filtration systems—such as reverse osmosis systems—may create wastewater that is fed to a drainage or sewage system. This waste or reject water contains contaminants filtered from the water. The backflow of this wastewater from the sewage system to the water filtration system is also undesirable. Accordingly, with these and other applications, it is desirable to provide protection against such backflow. Building codes and other government regulations may require that such protection be provided.
One device that can be used to prevent backflow is a check valve. A common construction uses a spring that forces a ball or other element against a port to seal off backflow through the port. When fluid flows in the proper direction, it pushes the ball and compresses the spring, thereby allowing fluid to flow through the port. However, if fluid attempts to backflow through the port, the flow is in the same direction of action as the spring, and the fluid and spring act together to force the ball against the port and thereby prevent such backflow.
A check valve can lose its ability to operate correctly due to e.g., hysteresis of the spring. In addition, the check valve is typically an additional, separate element that must be installed in a fluid system, thereby adding to the overall complexity and expense. As an additional item, the check valve will also consume additional space. For certain applications, such as a kitchen sink or within cabinetry, such additional space may be unavailable or its use for a check valve or other backflow prevention device may be undesirable.
Accordingly, a device for protecting against backflow in a fluid system would be desirable. More particularly, a device that can protect against backflow and that can be incorporated within a valve to provide additional functionality and space savings would be beneficial.